Catalytic composite particularly useful for the oxidation of mercaptans contained in a sour petroleum distillate

ABSTRACT

A catalytic composite comprising a metal chelate mercaptan oxidation catalyst and a quaternary ammonium salt impregnated on a solid adsorptive support is disclosed. The quaternary ammonium salt is represented by the structural formula ##STR1## wherein R is a hydrocarbon radical containing up to about 20 carbon atoms and selected from the group consisting of alkyl, cycloalkyl, aryl, alkaryl and aralkyl, R 1  is a substantially straight-chain alkyl radical containing from about 5 to about 20 carbon atoms, R 2  is selected from the group consisting of aryl, alkaryl, and aralkyl, and X is an anion selected from the group consisting of halide, nitrate, nitrite, sulfate, phosphate, acetate, citrate and tartrate. The catalytic composite is particularly adapted to the oxidation of mercaptans contained in a sour petroleum distillate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of a copending applicationSer. No. 880,723 filed Feb. 24, 1978 now U.S. Pat. No. 4,124,493.

This invention relates to a catalytic composite particularly adapted tothe conversion of difficultly oxidizable mercaptans contained in a sourpetroleum distillate. Processes for the treatment of sour petroleumdistillates wherein the distillate is treated in contact with anoxidation catalyst in the presence of an oxidizing agent at alkalinereaction conditions have become well known and widely practiced in thepetroleum refining industry. Said processes are typically designed toeffect the oxidation of offensive mercaptans contained in a sourpetroleum distillate with the formation of innocuous disulfides--aprocess commonly referred to as sweetening. Depending on the source ofthe petroleum from which the sour distillate was derived, the boilingrange of the distillate itself, and possibly the method of processingthe petroleum to produce the distillate, the distillates vary widelywith respect to the concentration, molecular weight and complexity ofthe mercaptans contained therein, and the sweetening process will varyaccordingly.

One such process relates to olefin-containing petroleum distillates.When said distillates are required to be maintained in storage for anylength of time, they advantageously contain an oxidation inhibitor toobviate gum formation. The inhibitor is typically an oil-solublephenylenediamine. When the olefin-containing distillates further containa relatively small concentration of the more readily oxidizablemercaptans, the phenylenediamine acts as a homogeneous oxygen transferagent and, in the presence of an alkaline reagent, promotes theoxidation of mercaptans and the formation of disulfides. It is to benoted that at least one-third of the mercaptans are consumed byinteraction with the olefin content of the sour distillate. The processis commonly referred to as inhibitor sweetening. The homogeneousphenylenediamine is not recoverable but is expended in the sweeteningprocess, and as the amount of the phenylenediamine required to effect aneconomical rate of oxidation becomes excessive, the process becomesineffective as a sweetening process and resort must be had to othermeans. It is known that inhibitor sweetening, which is essentially abatch type of process more suited to the treatment of sour distillatesin storage, functions only with respect to olefin-containingdistillates--the olefin being essential to the inhibitor sweeteningprocess. Over a period of time, usually measured in hours or days, thestored distillate may become doctor sweet depending on the complexityand the concentration of the mercaptans contained therein. While certainquaternary ammonium halides have been used in conjunction with thehomogeneous phenylenediamine catalyst to accelerate the sweeteningprocess as shown in U.S. Pat. No. 3,164,544, the process remains subjectto the general limitations of inhibitor sweetening. Thus, inhibitorsweetening is generally ineffective with respect to sour petroleumdistillates containing mercaptans other than primary and secondarymercaptans, and increasingly ineffective with respect to petroleumdistillates containing in excess of about 150 ppm. mercaptan sulfur.

Sour petroleum distillates that do not respond to inhibitor sweetening,i.e., those containing the higher molecular weight and/or more complexmercaptans, or higher mercaptan concentrations, are commonly treated incontact with a heterogenous metal phthalocyanine catalyst dispersed inan aqueous caustic solution to yield a doctor sweet product. The sourdistillate and the catalyst-containing aqueous caustic solution providea liquid-liquid system wherein mercaptans are converted to disulfides atthe interface of the immersible solutions in the presence of anoxidizing agent--usually air. This liquid-liquid system is invariablyemployed in a continuous type of operation requiring a substantiallylesser contact time than required of inhibitor sweetening. The metalphthalocyanine catalyst, which is recovered and recycled for continuoususe, is not limited to use in conjunction with an olefin-containingpetroleum distillate, but is equally effective with regard toolefin-free distillates to provide a doctor sweet product.

Certain of the higher boiling sour petroleum distillates, generallyboiling in excess of about 275° F., contain highly hindered branchedchain and aromatic thiols, and/or higher molecular weight tertiary andpolyfunctional mercaptans, which are at most only partially soluble inthe catalyst-containing caustic solution of the liquid-liquid treatingsystem. Sour petroleum distillates containing these more difficultlyoxidizable mercaptans are more effectively treated in contact with ametal phthalocyanine catalyst disposed or impregnated on a high surfacearea adsorptive support or carrier material--usually an activatedcharcoal. The distillate is treated in contact with the supported metalphthalocyanine catalyst at oxidation conditions in the presence of analkaline reagent. One such process is described in U.S. Pat. No.2,988,500. The oxidizing agent is most often air admixed with thedistillate to be treated, and the alkaline reagent is most often anaqueous caustic solution charged continuously to the process orintermittently as rquired to maintain the catalyst in a caustic-wettedstate.

It is an object of this invention to present a novel catalytic compositeparticularly useful in the treatment of sour petroleum distillatescontaining the more difficultly oxidizable mercaptans.

In one of its broad aspects, the present invention embodies a catalyticcomposite comprising a metal chelate mercaptan oxidation catalyst and aquaternary ammonium salt impregnated on a solid adsorptive support, saidquaternary ammonium salt being represented by the structural formula##STR2## wherein R is a hydrocarbon radical containing up to about 20carbon atoms and selected from the group consisting of alkyl,cycloalkyl, aryl, alkaryl and aralkyl, R₁ is a substantiallystraight-chain alkyl radical containing from about 5 to about 20 carbonatoms, R₂ is selected from the group consisting of aryl, alkaryl andaralkyl, and X is an anion selected from the group consisting ofchloride, bromide, iodide, fluoride, nitrate, nitrite, sulfate,phosphate, acetate, citrate and tartrate.

One of the more specific embodiments concerns a catalytic compositecomprising from about 0.1 to about 10 wt. % metal phthalocyanine andfrom about 1 to about 50 wt. % benzyldimethylalkylammonium chlorideimpregnated on an activated charcoal support, the alkyl substituent ofsaid benzyldimethylalkylammonium chloride being a substantially straightchain alkyl radical containing from about 5 to about 20 carbon atoms.

A still more specific embodiment of this invention relates to acatalytic composite comprising from about 0.1 to about 2 wt. % cobaltphthalocyanine monosulfonate and from about 5 to about 35 wt. %benzyldimethylalkylammonium chloride impregnated on an activatedcharcoal support, the alkyl substituent of saidbenzyldimethylalkylammonium chloride being a substantially straightchain alkyl radical containing from about 12 to about 18 carbon atoms.

Other objects and embodiments of this invention will become apparent inthe following detailed specification.

The metal chelate mercaptan oxidation catalyst employed as a componentof the catalytic composite of this invention can be any of the variousmetal chelates known to the treating art as effective to catalyze theoxidation of mercaptans contained in a sour petroleum distillate withthe formation of polysulfide oxidation products. Said chelates includethe metal compounds of tetrapyridinoporphyrazine described in U.S. Pat.No. 3,980,582, e.g., cobalt, tetrapyridinoporphyrazine; porphyrin andmetaloporphyrin catalysts as described in U.S. Pat. No. 2,966,453, e.g.,cobalt tetraphenylporphrin sulfonate; corriniod catalysts as describedin U.S. Pat. No. 3,252,892, e.g., cobalt corrin sulfonate; chelateorganometallic catalysts such as described in U.S. Pat. No. 2,918,426,e.g., the condensation product of an aminophenol and a metal of GroupVIII; and the like. Metal phthalocyanines are a preferred class of metalchelate mercaptan oxidation catalysts.

The metal phthalocyanines employed as a mercaptan oxidation catalystgenerally include magnesium phthalocyanine, titanium phthalocyanine,hafnium phthalocyanine, vanadium phthalocyanine, tantalumphthalocyanine, molybdenum phthalocyanine, manganese phthalocyanine,iron phthalocyanine, cobalt phthalocyanine, nickel phthalocyanine,platinum phthalocyanine, palladium phthalocyanine, copperphthalocyanine, silver phthalocyanine, zinc phthalocyanine, tinphthalocyanine and the like. Cobalt phthalocyanine and vanadiumphthalocyanine are particularly preferred. The metal phthalocyanine ismost frequently employed as a derivative thereof, the commerciallyavailable sulfonated derivatives, e.g., cobalt phthalocyaninemonosulfonate, cobalt phthalocyanine disulfonate or a mixture thereofbeing particularly preferred. The sulfonated derivatives may beprepared, for example, by reacting cobalt, vanadium or other metalphthalocyanine with fuming sulfuric acid. While the sulfonatedderivatives are preferred, it is understood that other derivatives,particularly the carboxylated derivatives, may be employed. Thecarboxylated derivatives are readily prepared by the action oftrichloroacetic acid on the metal phthalocyanine.

The quaternary ammonium salt component of the catalytic composite ofthis invention is represented by the structural formula ##STR3## whereinR is a hydrocarbon radical containing up to about 20 carbon atoms andselected from the group consisting of alkyl, cycloalkyl, aryl, alkaryland aralkyl, R₁ is a substantially straight chain alkyl radicalcontaining from about 5 to about 20 carbon atoms, R₂ is selected from agroup consisting of aryl, alkaryl and aralkyl and X is an anion selectedfrom the group consisting of halide, nitrate, nitrite, sulfate,phosphate, acetate, citrate and tartrate. R₁ is preferably an alkylradical containing from about 12 to about 18 carbon atoms, R₂ ispreferably benzyl, and X is preferably chloride. Preferred quaternaryammonium salts thus include benzyldimethyldodecylammonium chloride,benzyldimethyltetradecylammonium chloride,benzyldimethyhexadecylammonium chloride, benzyldimethyloctadecylammoniumchloride, and the like. Other suitable quaternary ammonium salts includephenyldimethylpentylammonium chloride, phenyldiethylpentylammoniumchloride, phenyldipropylpentylammonium chloride,phenyldimethylhexylammonium chloride, phenyldiethylhexylammoniumchloride, phenyldipropylhexylammonium chloride,phenyldimethyloctylammonium chloride, phenyldiethyloctylammoniumchloride, phenyldipropyloctylammonium chloride,phenyldimethyldecylammonium chloride, phenyldiethyldecylammoniumchloride, phenyldipropyldecylammonium chloride,phenyldimethyldodecylammonium chloride, phenyldiethyldodecylammoniumchloride, phenyldipropyldodecylammonium chloride,phenyldimethyltetradecylammonium chloride,phenyldiethyltetradecylammonium chloride,phenyldipropyltetradecylammonium chloride,phenyldimethylhexadecylammonium chloride, phenyldiethylhexadecylammoniumchloride, phenyldipropylhexadecylammonium chloride,phenyldimethyloctadecylammonium chloride, phenyldiethyloctadecylammoniumchloride, phenyldipropyloctadecylammonium chloride,phenyldimethyleicosylammonium chloride, phenyldiethyleicosylammoniumchloride, phenyldipropyleicosylammonium chloride,naphthyldimethylpentylammonium chloride, naphthyldiethylpentylammoniumchloride, naphthyldipropylpentylammonium chloride,naphthyldimethyhexylammonium chloride, naphthyldiethylhexylammoniumchloride, naphthyldipropylhexylammonium chloride,naphthyldimethyloctylammonium chloride, naphthyldiethyloctylammoniumchloride, naphthyldipropyloctylammonium chloride,naphthyldimethyldecylammonium chloride, naphthyldiethyldecylammoniumchloride, naphthyldipropyldecylammonium chloride,naphthyldimethyldodecylammonium chloride, naphthyldiethyldodecylammoniumchloride, naphthyldipropyldodecylammonium chloride,naphthyldimethyltetradecylammonium chloride,naphthyldiethyltetradecylammonium chloride,naphthyldipropyltetradecylammonium chloride,naphthyldimethylhexadecylammonium chloride,naphthyldiethylhexadecylammonium chloride,naphthyldipropylhexadecylammonium chloride,naphthyldimethyloctadecylammonium chloride,naphthyldiethyloctadecylammonium chloride,naphthyldipropyloctadecylammonium chloride, benzyldimethylpentylammoniumchloride, benzyldiethylpentylammonium chloride,benzyldipropylpentylammonium chloride, benzyldimethylhexylammoniumchloride, benzyldiethylhexylammonium chloride,benzyldipropylhexylammonium chloride, benzyldimethyloctylammoniumchloride, benzyldiethyloctylammonium chloride,benzyldipropyloctylammonium chloride, benzyldimethyldecylammoniumchloride, benzyldiethyldecylammonium chloride,benzyldipropyldecylammonium chloride, benzyldiethyldodecylammoniumchloride, benzyldipropyldodecylammonium chloride,benzyldiethyltetradecylammonium chloride,benzyldipropyltetradecylammonium chloride,benzyldiethylhexadecylammonium chloride, benzyldipropylhexadecylammoniumchloride, benzyldiethyloctadecylammonium chloride,benzyldipropyloctadecylammonium chloride, benzyldimethyleicosylammoniumchloride, benzyldiethyleicosylammonium chloride,benzyldipropyleicosylammonium chloride, tolyldimethylpentylammoniumchloride, tolyldiethylpentylammonium chloride,tolyldipropylpentylammonium chloride, tolyldimethylhexylammoniumchloride, tolyldiethylhexylammonium chloride, tolyldipropylhexylammoniumchloride, tolyldimethyloctylammonium chloride, tolyldiethyloctylammoniumchloride, tolyldipropyloctylammonium chloride,tolyldimethyldecylammonium chloride, tolyldiethyldecylammonium chloride,tolyldipropyldecylammonium chloride, tolyldimethyldodecylammoniumchloride, tolyldiethyldodecylammonium chloride,tolyldipropyldodecylammonium chloride, tolyldimethyltetradecylammoniumchloride, tolyldiethyltetradecylammonium chloride,tolyldipropyltetradecylammonium chloride, tolyldimethylhexadecylammoniumchloride, tolyldiethylhexadecylammonium chloride,tolyldipropylhexadecylammonium chloride, tolyldimethyloctadecylammoniumchloride, tolyldiethyloctadecylammonium chloride,tolyldipropyloctadecylammonium chloride, tolyldimethyleicosylammoniumchloride, tolyldiethyleicosylammonium chloride,tolyldipropyleicosylammonium chloride, diphenylmethylpentylammoniumchloride, diphenylethylpentylammonium chloride,diphenylpropylpentylammonium chloride, diphenylmethylhexylammoniumchloride, diphenylethylhexylammonium chloride,diphenylpropylhexylammonium chloride, diphenylmethyloctylammoniumchloride, diphenylethyloctylammonium chloride,diphenylpropyloctylammonium chloride, diphenylmethyldecylammoniumchloride, diphenylethyldecylammonium chloride,diphenylpropyldecylammonium chloride, diphenylmethyldodecylammoniumchloride, diphenylethyldodecylammonium chloride,diphenylpropyldodecylammonium chloride, diphenylmethyltetradecylammoniumchloride, diphenylethyltetradecylammonium chloride,diphenylpropyltetradecylammonium chloride,diphenylmethylhexadecylammonium chloride, diphenylethylhexadecylammoniumchloride, diphenylpropylhexadecylammonium chloride,diphenylmethyloctadecylammonium chloride, diphenylethyloctadecylammoniumchloride, diphenylpropyloctadecylammonium chloride,diphenylmethyleicosylammonium chloride, diphenylethyleicosylammoniumchloride, diphenylpropyleicosylammonium chloride, as well as thecorresponding fluoride, bromide, iodide, sulfate, nitrate, nitrite,phosphate, acetate, citrate and tartrate salts.

The preferred benzyldimethylalkylammonium chlorides are commerciallyavailable from the Mason Chemical Company under the tradename Maquats.However, said benzyldimethylalkylammonium chlorides can be prepared byinitially reacting ammonia and a C₁₂ -C₁₈ carboxylic acid in contactwith silica gel at about 500° C. to form a C₁₂ -C₁₈ nitrile. The nitrileis then reduced with hydrogen in contact with a nickel catalyst at about140° C. The resulting C₁₂ -C₁₈ amine is separated from the reactionmixture and reacted with a 2 molar excess of methyl chloride. Afterneutralization of the reaction mixture, the amine is further reactedwith 1 mole equivalent of benzyl chloride to yield the desiredbenzyldimethylalkylammonium chloride. The methyl chloride as well as thebenzyl chloride, is suitably reacted with the amine in methanolicsolution at a temperature of about 150° C. The product can be used as isor further treated over activated charcoal to remove impurities.

The solid adsorbent support or carrier material employed herein can beany of the well known solid adsorbent materials generally utilized as acatalyst support or carrier material. Preferred adsorbent materialsinclude the various charcoals produced by the destructive distillationof wood, peat, lignite, nutshells, bones, and other carbonaceous matter,and preferably such charcoals as have been heat treated or chemicallytreated or both, to form a highly porous particle structure of increasedadsorbent capacity, and generally defined as activated carbon orcharcoal. Said adsorbent materials also include the naturally occurringclays and silicates, e.g., diatomaceous earth, fuller's earth,kieselguhr, attapulgus clay, feldspar, montmorillonite, halloysite,kaolin, and the like, and also the naturally occurring or syntheticallyprepared refractory inorganic oxides such as alumina, silica, zirconia,thoria, boria, etc. or combinations thereof like silica-alumina,silica-zirconia, alumina-zirconia, etc. Any particular solid adsorbentmaterial is selected with regard to its stability under conditions ofits intended use. For example, in the treatment of a sour petroleumdistillate heretofore described, the solid adsorbent carrier materialshould be insoluble in, and otherwise inert to, the petroleum distillateat the alkaline reaction conditions existing in the treating zone. Inthe latter case, charcoal, and particularly, activated charcoal, ispreferred because of its capacity for metal phthalocyanine, and becauseof its stability under treating conditions.

The quaternary ammonium salts of this invention, as well as the metalchelate mercaptan oxidation catalyst, particularly the metalphthalocyanines, are readily adsorbed on the solid adsorbent support.The quaternary ammonium salt may comprise up to about 50 wt. % or moreof the catalytic composite. In the sweetening process hereincontemplated, the quaternary ammonium salt will suitably comprise fromabout 1 to about 50 wt. %, and preferably from about 5 to about 35 wt. %of the said composite. In general, up to about 25 wt. % metalphthalocyanine can be adsorbed on the solid adsorbent support and stillform a stable catalytic composite. A lesser amount in the range of fromabout 0.1 to about 10 wt. % generally forms a suitably active catalyticcomposite. The activity advantage derived from metal phthalocyanineconcentrations in excess of about 2 wt. % has not heretofore warranteduse of higher concentrations. However, in view of the significantincrease in activity derived from the use of the quaternary ammoniumsalt of this invention in conjunction with minimal metal phthalocyanineconcentrations, it is contemplated that the higher concentration willbecome effective to promote a further increase in the rate of mercaptanoxidation, particularly with regard to the hard to treat sour petroleumdistillates.

The quaternary ammonium salt and the metal chelate components can beimpregnated on the solid adsorbent support in any conventional orotherwise convenient manner, and said components can be impregnated onsaid support simultaneously from a common aqueous or alcoholic solutionand/or dispersion thereof, or separately and in any desired sequence.The impregnation process can be effected utilizing conventionaltechniques whereby the support in the form of spheres, pills, pellets,granules or other particles of uniform or irregular size or shape, issoaked, suspended, dipped one or more times, or otherwise immersed in anaqueous or alcoholic impregnating solution and/or dispersion to adsorb agiven quantity of the ammonium salt and metal chelate componentsthereon. One preferred method involves the use of a steam-jacketedrotary dryer. The adsorbent support is immersed in the impregnatingsolution and/or dispersion contained in the dryer and the support istumbled therein by the rotating motion of the dryer. Evaporation of thesolution in contact with the tumbling support is expedited by applyingsteam to the dryer jacket. In any case, the resulting composite isallowed to dry under ambient temperature conditions, or dried at anelevated temperature in an oven, or in a flow of hot gases, or in anyother suitable manner.

An alternative and convenient method for adsorbing the ammonium salt andmetal chelate components on the solid adsorbent support comprisespredisposing the support in a sour petroleum distillate treating zone orchamber as a fixed bed and passing the ammonium salt-metal chelateimpregnating solution and/or dispersion through the bed in order to formthe catalytic composite in situ. This method allows the solution and/ordispersion to be recycled one or more times to achieve a desiredconcentration of the ammonium salt and metal chelate components on theadsorbent support. In still another alternative method, the adsorbentmay be predisposed in said treating zone or chamber, and the zone orchamber thereafter filled with the impregnating solution and/ordispersion to soak the support for a predetermined period.

In the process of sweetening a sour petroleum distillate, it hasheretofore been the practice to oxidize the mercaptans contained thereinin the presence of an alkaline reagent. A supported mercaptan oxidationcatalyst is typically initially saturated with the alkaline reagent, andthe alkaline reagent thereafter passed in contact with the catalyst bed,continuously or intermittently as required, admixed with the sourpetroleum distillate. Any suitable alkaline reagent may be employed. Analkaline metal hydroxide in aqueous solution, e.g., sodium hydroxide inaqueous solution, is most often employed. The solution may furthercomprise a solubilizer to promote mercaptan solubility, e.g., alcohol,and especially methanol, ethanol, n-propanol, isopropanol, etc., andalso phenols, cresols, and the like. A particularly preferred alkalinereagent is an aqueous caustic solution comprising from about 2 to about30 wt. % sodium hydroxide. The solubilizer, when employed, is preferablymethanol, and the alkaline solution may suitably comprise from about 2to about 100 vol. % thereof. Sodium hydroxide and potassium hydroxideconstitute the preferred alkaline reagents, others including lithiumhydroxide, rubidium hydroxide and cesium hydroxide are also suitablyemployed.

The process of this invention can be effected in accordance with priorart treating conditions. The process is usually effected at ambienttemperature conditions, although higher temperatures up to about 105° C.are suitably employed. Pressures of up to about 1,000 psi or more areoperable, although atmospheric or substantially atmospheric pressuresare entirely suitable. Contact times equivalent to a liquid hourly spacevelocity of from about 0.5 to about 10 or more are effective to achievea desired reduction in the mercaptan content of a sour petroleumdistillate, an optimum contact time being dependent on the size of thetreating zone, the quantity of catalyst contained therein, and thecharacter of the distillate being treated.

As previously stated, sweetening of the sour petroleum distillate iseffected by oxidizing the mercaptan content thereof to disulfides.Accordingly, the process is effected in the presence of an oxidizingagent, preferably air, although oxygen or other oxygen-containing gasmay be employed. The sour petroleum distillate may be passed upwardly ordownwardy through the catalyst bed. The sour petroleum distillate maycontain sufficient entrained air, but generally added air is admixedwith the distillate and charged to the treating zone concurrentlytherewith. In some cases, it may be of advantage to charge the airseparately to the treating zone and countercurrent to the distillateseparately charged thereto.

The catalytic composite of this invention is both active and stable.Accordingly, the composite can be used in a fixed bed to treat largevolumes of sour petroleum distillates, especially those distillatescontaining the more difficultly oxidizable mercaptans. As heretoforementioned, the quaternary ammonium salt and metal phthalocyaninecomponents of the catalytic composite of this invention are readilyadsorbed on the solid adsorbent support component thereof. Thus, any ofthe said quaternary ammonium salt or metal phthalocyanine componentswhich may in time be leached from the support and carried away in thereactant stream can be easily restored to the catalytic composite insitu by introducing either or both of said components to the sweeteningprocess, for example, in admixture with the alkaline reagent, to beadsorbed on the solid adsorbent support in the treating zone.

The following examples are presented in illustration of one preferredembodiment of this invention and are not intended as an undue limitationon the generally broad scope of the invention as set out in the appendedclaims.

EXAMPLE

In the preparation of the catalytic composite of this invention, animpregnating solution and/or dispersion was formulated by adding 0.75gms of cobalt phthalocyanine monosulfonate and 23.5 gms. of a 50%alcoholic solution of dimethylbenzylalkylammonium chloride to 250 ml. ofdeionized water in a rotary steam evaporator. Thebenzyldimethylalkylammonium chloride consisted ofbenzyldimethyldodecylammonium chloride (61%),benzyldimethyltetradecylammonium chloride (23%),benzyldimethylhexadecylammonium chloride (11%), andbenzyldimethyloctadecylammonium chloride. About 250 cc of 10×30 meshactivated charcoal particles were immersed in the impregnating solutionand tumbled therein for about 1 hour by the rotating motion of theevaporator. Steam was thereafter applied to the evaporator jacket, andthe impregnating solution was evaporated to dryness in contact with thetumbling charcoal particles over a one hour period.

The catalytic composite thus prepared, hereinafter referred to asCatalyst A, was subjected to a comparative evaluation test relative to a"standard" catalyst. The "standard" catalyst, hereinafter referred to asCatalyst B, was prepared substantially as described but without thebenzyldimethylalkylammonium chloride component.

The comparative evaluation test consisted in processing a sour kerosenedownflow through 100 cc of catalyst disposed as a fixed bed in avertical tubular reactor. The kerosene was charged at an LHSV of about0.5 under about 35 psig of air--sufficient to provide about 1.5 timesthe stoichiometric amount of oxygen required to oxidize the mercaptanscontained in the kerosene. In each case, the catalyst bed was initiallywetted with 10 cc of an 8% aqueous sodium hydroxide solution, 10 cc ofsaid solution being subsequently charged to the catalyst bed at 12 hourintervals admixed with the kerosene charged thereto. The treatedkerosene, which initially contained 533 ppm. mercaptan sulfur, wasanalyzed periodically for mercaptan sulfur. The mercaptan sulfur contentof the treated kerosene was plotted against the hours on stream toprovide a curve from which the data set out in the table below wasderived.

                  TABLE                                                           ______________________________________                                                    Mercaptan Sulfur, wt. ppm.                                        Time, hrs.    Catalyst A   Catalyst B                                         ______________________________________                                         50            5           36                                                 100            9           31                                                 150           11           31                                                 200           11           31                                                 250           11           31                                                 ______________________________________                                    

I claim as my invention:
 1. A catalytic composite comprising a metalchelate mercaptan oxidation catalyst and a quaternary ammonium saltimpregnated on a solid adsorptive support, said quaternary ammonium saltbeing represented by the structural formula ##STR4## wherein R is ahydrocarbon radical containing up to about 20 carbon atoms and selectedfrom the group consisting of alkyl, cycloalkyl, aryl, alkaryl andaralkyl, R₁ is a substantially straight chain alkyl radical containingfrom about 5 to about 20 carbon atoms, R₂ is selected from the groupconsisting of aryl, alkaryl and aralkyl, and X is an anion selected fromthe group consisting of chloride, bromide, iodide, fluoride, nitrate,nitrite, sulfate, phosphate, acetate, citrate and tartrate.
 2. Thecatalytic composite of claim 1 further characterized in that saidquaternary ammonium component comprises from about 1 to about 50 wt. %of said catalytic composite.
 3. The catalytic composite of claim 1further characterized in that said quaternary ammonium componentcomprises from about 5 to about 35 wt. % of said catalytic composite. 4.The catalytic composite of claim 1 further characterized in that R₁ is asubstantially straight chain alkyl radical containing from about 12 toabout 18 carbon atoms.
 5. The catalytic composite of claim 1 furthercharacterized in that R₂ is benzyl.
 6. The catalytic composite of claim1 further characterized in that said quaternary ammonium salt is aquaternary ammonium halide.
 7. The catalytic composite of claim 1further characterized in that said quaternary ammonium salt is aquaternary ammonium chloride.
 8. The catalytic composite of claim 1further characterized in that said quaternary ammonium salt isbenzyldimethyldodecylammonium chloride.
 9. The catalytic composite ofclaim 1 further characterized in that said quaternary ammonium salt isbenzyldimethyltetradecylammonium chloride.
 10. The catalytic compositeof claim 1 further characterized in that said quaternary ammonium saltis benzyldimethylhexadecylammonium chloride.
 11. The catalytic compositeof claim 1 further characterized in that said quaternary ammonium saltis benzyldimethyloctadecylammonium chloride.
 12. The catalytic compositeof claim 1 further characterized in that said solid adsorptive supportis an activated charcoal.
 13. The catalytic composite of claim 1 furthercharacterized in that said metal chelate mercaptan oxidation catalyst isa metal phthalocyanine.
 14. The catalytic composite of claim 1 furthercharacterized in that said metal chelate mercaptan oxidation catalystcomprises from about 0.1 to about 10 wt. % of said catalytic composite.15. The catalytic composite of claim 1 further characterized in thatsaid metal chelate mercaptan oxidation catalyst comprises from about 0.1to about 2 wt. % of said catalytic composite.
 16. The catalyticcomposite of claim 1 further characterized in that said metal chelatemercaptan oxidation catalyst is a cobalt phthalocyanine.
 17. Thecatalytic composite of claim 1 further characterized in that said metalchelate mercaptan oxidation catalyst is a vanadium phthalocyanine. 18.The catalytic composite of claim 1 further characterized in that saidmetal chelate mercaptan oxidation catalyst is cobalt phthalocyaninemonosulfonate.